This invention is in the field of improved integrated circuit structures and specifically in the field of miniaturized dielectrically isolated integrated circuit structures.
Solid-state devices in general and semiconductor devices in particular must have exacting surface properties for successful operations. These devices therefore often fail by surface or stress-related failure mechanisms. The surface of a PN, P+N, P−N, PN+, PN−, PI, NI, metal-oxide, metal-semiconductor, oxide-semiconductor, interfacial rectifying barrier region, heterojunction between different semiconductor materials such as Si on SiC or diamond, or other optoelectromagnetically active signal-translating region (including several coacting, closely spaced rectifying barriers) is especially sensitive to the ambient or contacting materials, contaminants, impurities, or submicron floating or rubbing dust particles. While not limited thereto, the invention is herein mostly described as examples applied to semiconductor devices each having a PN junction as its optoelectromagnetically active region.
The U.S. Pat. No. 3,585,714 describes new methods for simultaneously achieving device isolation, mismatched composite materials shaping to withstand severe thermal mismatch or chemical reaction induced stresses, junction surface passivation, novel differential expansion of the junction region peripheral surface, physical or optoelectromagnetical exposure of material hidden underneath the junction, high-density integrated circuits witch round-bottomed, intersecting and isolating grooves, and/or greatly expanded peripheral surface for optoelectrical communication or for the otherwise difficult or impossible yet large (relative to the narrow junction width) electrical contacts. Many advantages are thus obtained including: enhanced device reliability particularly during thermomechanical cyclings or in-situ compound formations; increased yield; decreased cost; improved junction region surface passivation; complete device isolation; increased packing density in integrated circuits; increased switching speed; reduced nose, instability, leakage current, and electrical shorts; improved breakdown voltage or other device characteristics; controlled carriers generation, movement, and recombination at or near the junction region peripheral surface; and regulated optoelectromagnetic interaction of the active region with the ambient or contacting material.
The same U.S. patent describes fully the techniques of selective precision material removal by special chemical etching, mechanical polishing with real-time feed-back, or particles bombarding means to achieve microscopically precisely (micron accuracy), differentially expanded junction region peripheral surface of microscopically precise (micron accuracy) shape, size, and location. Such a surface is, furthermore, resistant to surface stress, mobile ions, floating dust particles, and even micron-size rubbing contaminants and, hence, greatly reduces surface failures of the device due to surface microcracks, or micron or submicron dust particles in the environment.
However, such an expanded peripheral surface, being bare, is still not perfectly passivated. Surface layers of inert materials must, therefore, be applied or added onto the differentially expanded peripheral surface for added protection. The same patent also teaches the in-situ formation techniques of the isolating grooves made by thermal oxidation or nitridation.
Unfortunately, these surface layers are far from being perfect or even inert, but are often full of pinholes, microcracks, and other defects. In addition, as pointed out in the '714 patent, these layers must, at the same time, be both thick (but non-flaking) for good protection and yet thin (but non-cracking) for reduced mismatch stresses. They must also be permanently, chemically, and continuously yet firmly bonded to the underlying solid-state materials. These surface layers cannot, therefore, always or in all respects, be inert or neutral. These layers may, for example, be chemically active by introducing contaminants, diffusants, unwanted impurities, or chemical reactants. They may also be physically active by creating intolerable mismatch stresses and strains, microcracks, dislocations, or other physical defects in the solid state device. These layers may even be electrically active by providing unwanted dopants, carrier traps, barrier regions, shorting paths, or inductively-coupled and capacitively-coupled surface streaks or films.